Endowment Mortgages

Anyone taking out an endowment mortgage to buy a house borrows money from a bank promising to repay the loan after a 25 or so years, and raises the money to repay the loan by investing a certain amount of money each year, the amount being calculated so that after 25 years, the total investment will pay off the loan.
Suppose an amount £200,000 is borrowed. The bank will charge interest on this loan at

\[r_1\]

%, so that after 25 years the amount of money that needs to be repaid is